Akein Scott, 19, was arrested Wednesday night. / Handout

by John Bacon and Katharine Lackey, USA TODAY

by John Bacon and Katharine Lackey, USA TODAY

Police arrested a second suspect Thursday in the New Orleans shooting that injured 20 at a Mother's Day parade, as the city's mayor called on residents to help end violence.

Shawn Scott, 24, is the brother of 19-year-old Akein Scott, who was arrested Wednesday night in the shooting, Police Chief Ronal Serpas said, according to the AP.

Both face 20 counts of attempted second-degree murder, and Serpas said investigators believe the Scotts worked together in the shooting.

"We all came back here to make it clear that the culture of death and violence on the streets of New Orleans is unnatural, it's unacceptable and the people of New Orleans have had enough," Mayor Mitch Landrieu said at a news conference near the city's French Quarter.

Bail for Akein Scott was set at $10 million, Landrieu said.

"This is a clear signal that this type of disregard for human life on the streets of New Orleans is always unacceptable," he said.

At a court appearance Thursday, Akein Scott, shackled and wearing an orange prison jumpsuit, stood silently as his court-appointed attorney handled the proceedings.

Prosecutors said a witness picked out a photo of Akein Scott, 19, from a lineup. An arrest affidavit said the unidentified witness told investigators that Akein Scott was the person seen in a surveillance video that police released to the public as they searched for him for three days.

That surveillance video of the shooting scene Sunday showed the crowd fleeing and some people falling down as a man in a white T-shirt and dark pants fled. On Monday, Serpas said Akein Scott had been identified by multiple people as the possible gunman.

Earlier, police had said that three gunmen were involved and that at least two different weapons were used. Police offered a $10,000 reward in the case.

The event was known locally as a "second-line parade" -- a loose processions in which people dance down the street, often following behind a brass band. They can be impromptu or planned and are sometimes described as moving block parties.

The parade drew up to 400 people, including police officers and was about two blocks long, police said. Wounded were 10 men and seven women as well as a boy and a girl, both 10, who suffered graze wounds. One person was injured trying to flee the shooting.

Police previously said Akein Scott had an arrest record involving drug and weapon charges. Court records show some had been dropped but he was facing a felony charge of illegally carrying a weapon while in possession of a controlled dangerous substance.